Flow guiding body for a gas turbine combustion chamber

ABSTRACT

A flow-guiding body is designed as a pointed, substantially conical molded shell. The projection of its base surface is formed by a straight line and by a curve that interconnects the ends of the straight line. The curve forms no significant angles. The molded shell faces with its point the fluid flow that hits its outer side and may be used as a mixing element for gaseous fuel and air, as an air sprayer with flame-holder, as a mixing element for admixed air in combustion chambers, as a swirling element or as a shell-shaped air sprayer combined with a fuel film generator or a fuel pressure spraying nozzle.

BACKGROUND AND SUMMARY OF THE INVENTION

The invention relates to a flow guiding body on a gas turbine combustionchamber for spinning an impinging air flow, consisting of at least oneacutely tapering molded shell of an essentially conical design, whosesurface area projection is formed by at least one straight line as wellas an arbitrary curve connecting the end points of the straight line.The molded shell faces the air flow impinging on the outer sideessentially with its tip.

From European Patent document EP-A-0 063 729, a comparable flow guidingbody is known as an arrangement for inverting and mixing flowingsubstances.

On gas turbine combustion chambers, particularly for aircraft engines,so-called airblast atomizers are known which have two or more coaxialring ducts through which the air mass delivered by the compressor flowswith different spins. In this context, a mixing with fuel has becomeknown. In this case, two air ducts are separated by a sharply taperingcircular ring to which a fuel film is applied. The fuel film is drivenby the air masses to the end edge of the circular ring and is atomizedthere. In the close area of the atomization edge, the fuel drop sprayhas a boundary-wake characteristic, which results in a poor homogeneityof the resulting fuel air mixture.

Furthermore, a flow guiding body which has an acutely tapering moldedshell is known in connection with a fuel feeding system for a combustionchamber from European Patent document EP-A-0 619 456, and in connectionwith a premixing burner from European Patent document EP-A-0 619 457.

Also, on gas turbines it is known to feed the mixing air for thedifferent combustion zones of a combustion chamber through plain orplunged holes in the combustion chamber wall. Frequently, this takesplace in that the individual air jets which penetrate the differentholes in the combustion chamber wall meet in a stagnation point andlocally cause a high turbulence there. However, in the interior of thecombustion chamber, hot gas situated in the interior flows around theblown-in air jets in the manner of a massive rod so that, in the area inwhich the hot gas and the admixed air meet, there will be no optimalmixing of air. A mixing occurs only in the boundary layer area betweenthe admixed air jet and the hot gas. It is known that this so-called hotgas slip through the hole cross-section of a combustion chamber isrelatively high.

For improving the mixing process of gases in or on gas turbinecombustion chambers, so-called "delta wings" have also become known. Inthis respect, reference is made, for example, to European Patentdocument EP 0 623 786 A1 or U.S. Pat. No. 3,974,646. Such delta wingsare sharp-edged bodies which divide an impinging flow field into twopartial flows each having a swirl axis such that the swirl axes areconvergent. The mixing processes which can be achieved in this mannerare not completely satisfactory because of this convergent swirlformation.

It is therefore an object of the invention to indicate measures by whichmixing processes of gases in gas turbine combustion chambers can beimproved. In particular, non-convergent and preferably divergentlyextending swirl axes are to be generated downstream of the flow guidingbody.

For achieving this object, the present invention provides a flow guidingbody on a gas turbine combustion chamber for spinning air flow,consisting of at least one acutely tapering molded shell of anessentially conical design, whose surface area projection is formed byat least one straight line as well as an arbitrary curve connecting theend points of the straight line. The molded shell, essentially with itstip, faces the air flow impinging on the outer side. Advantageousdevelopments and further developments are described herein.

The invention will be explained in detail by means of preferredembodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view for explaining the principles of only oneflow guiding body (molded shell) as well as of an impinging fluid flow;

FIG. 2 is a sectional view of the shell perpendicular to the main flowdirection showing the swirl field induced by the molding shell;

FIG. 3 is a lateral view of the molded shell or of the flow guiding bodywhich shows the angle of attack, the generating angle, as well as thetrajectory of individual flow lines;

FIG. 4 is a top view of the molded shell or of the flow guiding bodyshowing schematically a pair of vortices featuring vortex breakdown;

FIG. 5 is a view of a so-called double shell atomizer, consistingessentially of two flow guiding bodies, for explaining the principles ofarrangement;

FIG. 6 is a lateral view of a first application according to theinvention of such a flow guiding body on a gas turbine combustionchamber, such a molded shell being shown in the area of the admixing airholes of a gas turbine combustion chamber wall;

FIG. 7 is a view taken in the direction X of FIG. 6;

FIG. 8 is a lateral sectional view of a use of a flow guiding bodyaccording to the invention with a so-called fuel film layer on a gasturbine combustion chamber;

FIG. 9 is a view taken in the direction of Y from FIG. 8;

FIG. 10 is a view taken in the direction of Z from FIG. 8;

FIG. 11 is a view of another embodiment showing a fuel film layeraccording to the invention on a gas turbine combustion chamber;

FIG. 12 is a sectional view taken along line A--A from FIG. 11;

FIG. 13 is a view of another variant of a double shell atomizer having afuel film layer according to the invention; and

FIG. 14 is a sectional view taken along line B--B from FIG. 13.

DETAILED DESCRIPTION OF THE DRAWINGS

In all figures, the so-called flow guiding body has the referencenumber 1. It is always a molded shell of an essentially conical shape.The projected surface area 2 of this molded shell 1, whose interior ishollow, consists of a straight line 3a and of an arbitrary curve 3bwhich connects the end points of the straight line. In this case, themolded shell 1 is formed by the generated surface which connects thecurve 3b with the tip 4 of the molded shell 1. However, the linesextending from the tip 4 to the curve 3b do not necessarily have to bestraight but may be curved themselves. Corresponding to the respectiverequirements, the shape of this molded shell 1 can be freely selected;that is, in a test series, the respective most suitable shape of thecurve 3b as well as the respective most suitable value of the so-calledgenerating angle α of the cone formed by the molded shell 1 can bedetermined for the respective application purpose of this flow guidingbody according to the invention. The best results with respect to theoccurring flow field downstream of the flow guiding body 1 were achievedwhen the curve 3b did not have significant corner points; that is, withthe exception of the marginal edges, the surface of the flow guidingbody does not have other shape edges. The above-mentioned generatorangle α, which is the result of the constructive design, is explicitlyillustrated in FIG. 3.

FIG. 3 also shows the so-called angle of attack β by which the plane 5of the molded shell 1 defined by the tip 4 as well as by the straightline 3a is inclined with respect to the approach flow direction of thefluid flow. The flow impinging on the flow guiding body or the moldedshell 1 is illustrated by the flow vector 6. As illustrated, the fluidflow 6 flows against the molded shell 1 on its convex side, in whichcase the flow lines 7 are formed which are outlined in FIGS. 1, 3.

On the concave side of the molded shell 1, a swirling flow field isformed which is illustrated as a sectional view in FIG. 2perpendicularly to the main flow direction of the fluid flow 6. Thisswirl field has two vortex cones 8 which rotate in opposite directions.Because of the design, particularly of the curve 3b, these two vortexcones 8 flow apart downstream of the flow guiding body 3; that is, theydiverge. To this extent, this flow guiding body 1 differs significantlyfrom a delta wing which is known per se and which generates convergingvortex cones.

The circulation of the vortex cones 8 depends on the setting angle β. Ifthe swirl is sufficiently high, the vortex cones 8 may break downdownstream of the molded shell 1, as illustrated in FIG. 4. In thiscase, a recirculation zone is formed which has an inner boundary surface9a to the centrally continuing main fluid flow. In addition, therotating fluid has an outer boundary surface 9b to the surrounding mainfluid flow which is displaced only with a curving of its flow lines.

FIG. 5 illustrates a preferred application of a flow guiding bodyaccording to the invention. In this case, two molded shells 1 arearranged adjacent to one another, but spaced apart from one another, andare surrounded by a housing 10 which is illustrated in a broken-openmanner. Each of the two molded shells 1 is set by the angle of attack βwith respect to the horizontal line which is identical to the flowdirection of the fluid flow, such that the planes 5 of these moldedshells 1, which were defined in FIG. 3, enclose the angle 2β between oneanother. This so-called "double-shell atomizer", which is illustrated inFIG. 5 and which therefore essentially consists of two flow guidingbodies according to the invention, represents an air sprayer with aflame holder, in which case liquid fuel is usefully applied to theconvex side of the two molded shells 1. As desired, the flow develops onthe rear of the molded shells 1, the fluid flow passing through betweenthese molded shells 1 through the angle segment described by the angle2β essentially on the left side and the right side of the bisecting lineof the molded shells. Deviating from the illustrated arrangement, thetwo shells 1 may also have a common tip 4.

In addition, gaseous or solid fuels may also be applied to the convexsides or outer sides of the molded shells 1. The illustrated arrangementthen acts as a mixer with a flame holder. In each case, a stabilizing ofthe flame will be achieved as the result of the recirculation zonewithin the split-open swirl twists (compare reference number 8)explained in conjunction with FIG. 4.

If, in addition, the swirling flow field of the molded shell or moldedshells 1 is set perpendicularly to a second main flow, a fast mixing ofair in gas turbine combustion chambers can, for example, be achieved.This second main flow represents the hot gas and is pulled into therecirculation zone of the broken down vortex cones 8. In this case, thehot gas mixes with the fresh gas on the boundary surfaces 9a, 9b(compare FIG. 4). FIGS. 6 and 7 show how a molded shell 1 according tothe invention can be arranged on the combustion chamber wall of a gasturbine in order to mix the admixed air optimally with the hot gaswithin the combustion chamber.

In FIGS. 6 and 7, the molded shell again has the reference number 1,while the combustion chamber wall has the reference number 11. Withinthe combustion chamber 12 bounded by the combustion chamber wall 11, thehot gas flows in the direction of the arrow 13. As known, admixed air isto be added to this hot gas flow 13. In this case, the mixing air flow 6is guided to approach as fluid flow impinging on the molded shell 1outside the combustion chamber 12 along the combustion chamber wall 11and can enter the combustion chamber 12 by way of an opening 14 in thecombustion chamber wall 11. In order to achieve the desired flow of theadmixed air flow 6, the molded shell 1 is surrounded by a scoop 15 whichcatches a portion of the arriving air flow 6 and diverts it in thedirection of the opening 14. For this purpose, the curved scoop 15 isarranged on the outer side of the combustion chamber wall 11 such thatthe opening 14 is surrounded.

This arrangement has the following purpose. While, in the case of theknown state of the art, the mixing of mixing air frequently takes placesuch that two or more air jets meet in a stagnation point and generate aturbulence there causing a strong hot gas slip between the air jets, inthe case of the arrangement according to the invention, the admixed airis swirling. The disadvantage which exists in the known state of the artwhich is that the air jets will split into air bubbles in the stagnationpoint area, which are carried away by the hot gas flow and therefore mixslowly, is avoided by means of a molded shell according to the inventionwhich operates as a swirl generator. As explained above, as well ashere, vortex cones 8 are generated by the molded shell 1 which breakdown when the swirl is sufficiently high, whereby the flow fieldillustrated in FIG. 6 is formed, with the recirculation zone 16 which issurrounded by the admixed air 17. The improvement with respect to themixing effect in comparison to the known state of the art is achieved bythe following effects. The cold admixed air 17 again forms an outerboundary surface 9b with the hot gas flow 13. Since the admixed air 17is highly swirling and has a high density in comparison to the fuel gas13, centrifugal and lift forces in the area of these boundary surfaces9b result in a fast and intensive rearrangement of both air masses whichlead to a fine-grained turbulence and a fast mixing. The area of theboundary surface 9b is many times as large as the surface between thehot gas and the admixed air formed in the case of the previous state ofthe art. This considerably reduces the hot gas slip through the admixingplane.

Another application of a molded shell 1 according to the invention, or aflow guiding body according to the invention, is illustrated in FIGS. 8to 10. Here also, the molded shell 1 is arranged in the flow path of twofluid flows, specifically of an air flow 6 as well as of a fuel flow 20and acts as a so-called "shell atomizer" for a fuel injector. Asillustrated in FIGS. 8, 9, in this case, the molded shell 1 is againsurrounded by a jacket-shaped scoop 15 in which the fuel film layer 21is arranged. The fuel film layer 21 has a fuel duct 22 which ends in aflat funnel 23 (see FIG. 10). As in the previous embodiments, the fluidflow 6 also flows against the illustrated shell atomizer arrangement.

For the function of the fuel film layer 21, it is important that, asillustrated in FIG. 9, the latter is situated in the plane of symmetryof the molded shell 1. Furthermore, it is important that the opening orthe flat funnel 23 of the film layer 21 is situated at a narrow distancefrom the surface of the molded shell 1, as illustrated in FIG. 8. As aresult, it is achieved that the emerging fuel flow 20, immediately afterleaving the film layer 21, is diverted without any atomization, onto thesurface/contour of the molded shell 1. As a result, a desired fueldistribution can be adjusted on the molded shell 1. FIG. 10 is the viewtaken in the direction of arrow Z from FIG. 8 of the fuel film layer 21.The fuel duct 22 as well as the flat funnel 23 are visible. Expediently,the outer contour of the film injector 21 is shaped aerodynamically, asillustrated.

Instead of a fuel film generator, one or several fuel pressure atomizerswith an arbitrary atomizing characteristic can also be arranged inconnection with a molded shell 1 (flow guiding body) according to theinvention in order to achieve a favorable air-fuel mixing. Analogouslyto the film generator, a pressure atomizer also applies fuel to theconvex side of the molded shell 1.

FIGS. 11 and 13 show additional embodiments of a double shell atomizerwhich consists of two molded shells 2 and a fuel film layer 21. As analternative, pressure atomizers can be provided in place of the fuelfilm layer. FIGS. 12 and 14 are corresponding sectional views of FIGS.11 and 13, respectively. In this case, FIG. 11 shows a double shellatomizer which is acted upon on two sides and has two molded shells,similar to FIG. 5. In a suitable film generator 21, the fuel isdistributed to two ducts 22 (here without any flat funnel 23). However,it is also possible to act upon the double shell atomizer only on oneside, as illustrated by FIGS. 12 and 14.

Thus, the flow guiding body according to the invention and the moldedshell 1 according to the invention, in the last-discussed embodiments,therefore operate in connection with a fuel film generator 21 as a shellatomizer. In this case the fuel can be fed through one or more fuelducts 22. The fuel ducts 22 optionally lead into one or more flatfunnels 23, and the sprayer or the molded shell 1 being arranged at anarrow distance form the flat funnel 23 or form the mouth of the ducts22. The film generator 21 is situated in the plane of symmetry of themolded shell(s). In addition, a flow guiding body or a molded shell 1according to the invention can also be used as a swirling element whichwill then particularly consist of one or more arbitrarily shaped moldedshells 1 as well as of one or more matching scoops 15. This arrangementcan be used for the admixing and swirling of cold air in the case of gasturbine combustion chambers. This arrangement may be mounted at anypoint on the flame tube of arbitrary combustion chambers in anyposition. Generally, this (these) conical molded shell(s) of the shapeillustrated in FIG. 1 may have any cross-section, in which case the jetsleading from the tip 4 to the base or base surface 2 of the conicalcutout do not have to be straight lines. As explained in detail, thismolded shell 1 can be used as an air sprayer for any liquid fuels.However, the use as a mixing element and flame holder is also possiblewhen gaseous or powdered or granulated solid fuels of any type are used.In addition, naturally, any different gas or fluid flows can also bemixed with one another.

Although the invention has been described and illustrated in detail, itis to be clearly understood that the same is by way of illustration andexample, and is not to be taken by way of limitation. The spirit andscope of the present invention are to be limited only by the terms ofthe appended claims.

What is claimed is:
 1. Flow guiding body on a gas turbine combustionchamber for swirling an impinging air flow, comprising:at least oneacutely tapering molded shell having a substantially conical design, asurface area projection of said molded shell being formed by at leastone straight line as well as an arbitrary curve which connects endpoints of said one straight line; wherein a tip of said molded shellfaces the impinging air flow which impinges on an outer surface of saidmolded shell; a scoop arranged on an outer side of a wall of saidcombustion chamber, said scoop surrounding said molded shell such that,by way of an opening enclosed by said scoop, the impinging air flow isadmixed to a hot gas flow flowing in said combustion chamber.
 2. Flowguiding body according to claim 1, wherein a plane of said molded shelldefined by said tip and said straight line is inclined with respect toan approach flow direction of the impinging air flow.
 3. Flow guidingbody according to claim 1, further comprising at least one additionalmolded shell arranged adjacent to the acutely tapering molded shell butspaced apart from one another at least in areas.
 4. Flow guiding bodyaccording to claim 2, further comprising at least one additional moldedshell arranged adjacent to the acutely tapering molded shell but spacedapart from one another at least in areas.
 5. Flow guiding body on a gasturbine combustion chamber for swirling an impinging air flow,comprising:at least one acutely tapering molded shell having asubstantially conical design, a surface area projection thereof beingformed by at least one straight line as well as an arbitrary curveconnecting end points of said one straight line; wherein said moldedshell has a tip which faces the impinging air flow which impinges on anouter surface of said molded shell; a scoop arranged to surround saidmolded shell; one of a fuel film layer and a fuel pressure atomizercombined with said scoop, wherein said fuel is applied to the outersurface of said molded shell, said fuel being fed to said combustionchamber together with the impinging air flow.
 6. Flow guiding bodyaccording to claim 5, wherein a plane of said molded shell defined bysaid tip and said straight line is inclined with respect to an approachflow direction of the impinging air flow.
 7. Flow guiding body accordingto claim 5, further comprising at least one additional molded shellarranged adjacent to the acutely tapering molded shell but spaced apartfrom one another at least in areas.
 8. Flow guiding body according toclaim 6, further comprising at least one additional molded shellarranged adjacent to the acutely tapering molded shell but spaced apartfrom one another at least in areas.
 9. A mixing apparatus for acombustion chamber, comprising:a molded shell having a substantiallyconical design, a tip of said molded shell facing an impinging air flow;an air scoop surrounding said molded shell, said air scoop beingarranged on an outer wall of the combustion chamber to enclose anopening, through which opening the impinging air flow is fed into andadmixed to a hot gas flow flowing in said combustion chamber.
 10. A fuelfeed device for a combustion chamber, comprising:a molded shell having asubstantially conical design, a tip of said molded shell facing animpinging air flow; an air scoop surrounding said molded shell; one of afuel film layer and a fuel pressure atomizer combined with said moldedshell; wherein fuel applied to an outer surface of said molded shellfrom said one of said fuel film layer and said fuel pressure atomizer isfed to the combustion chamber together with the impinging air flow.